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<div class="moz-cite-prefix">On 11/12/2013 7:09 AM, luke.leighton
wrote:<br>
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cite="mid:CAPweEDwZyRDr2CAdP7s6+Y7+uDvHpwSVh-9vH=a2Gj2zmHssMw@mail.gmail.com"
type="cite">
<pre wrap="">On Mon, Nov 11, 2013 at 2:10 AM, Christopher Havel
<a class="moz-txt-link-rfc2396E" href="mailto:laserhawk64@gmail.com"><laserhawk64@gmail.com></a> wrote:
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<pre wrap="">On 11/10/2013 9:08 PM, luke.leighton wrote:
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apologies to everyone on the list - you may have noticed i'm using
brief and curt language at the moment. it's not personal: i just have
far less time available and have to be very focussed.
l.
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Sorry to hear you're so busy. Can I help? :D
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yes. i thought of something.
<a class="moz-txt-link-freetext" href="http://permalink.gmane.org/gmane.comp.hardware.netbook.arm/7597">http://permalink.gmane.org/gmane.comp.hardware.netbook.arm/7597</a>
could you investigate, find some "educational" style electronics
explanations online, as to why henrik's recommendation to use a
pull-up resistor to 3.3V and a reversed-diode between the Tx UART and
incoming Rx actually works? i'm attaching a small diagram showing the
circuit.
it can then be added here:
<a class="moz-txt-link-freetext" href="http://elinux.org/Embedded_Open_Modular_Architecture/EOMA-68#Requirements_for_UART">http://elinux.org/Embedded_Open_Modular_Architecture/EOMA-68#Requirements_for_UART</a>
also i think.... to avoid too big a voltage-drop it should be a zener
diode otherwise it might interfere with the thresholds.
basically i think the way it works is that 0 logic level on UART is
"positive voltage", and the Tx line "sucks" current down to GND in
order to indicate a "1". therefore, normally (i.e. without the diode)
current would be flowing *from* Rx *to* Tx if Tx is held at GND to
indicate a "1"... so putting the diode in the circuit is... well...
normal!
l.
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Try this :) it popped up on Google pretty quickly --> <a
href="http://www.hobbytronics.co.uk/schottky-logic-level-conversion">http://www.hobbytronics.co.uk/schottky-logic-level-conversion</a>
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